With the development of technologies in the communication field, Internet Protocol (IP) multimedia subsystem (IMS) will become the fixed and mobile core network of the next generation, and the development tendency and network evolution process of the diversities of access technology and service-providing, bearer by IP, and core network being integrated into IMS will emerge. Users will have better service experiences in the IMS network.
User identities used in a current IMS network mainly include IP multimedia private user identities (IMPIs) and IP multimedia public user identities (IMPUs). These user identities are stored in a home subscriber server (HSS) by subscription. When a user makes relevant service operation, relevant entities in the network, such as an interrogating call session control function (I-CSCF), a serving call session control function (S-CSCF), and an application server (AS), obtain subscription data of the relevant user from HSS via user identity.
The relationships between user identities and between user identity and subscription data in IMS are relatively complicated, in which:
One IMS subscription includes all subscription information that might be delivered via a Cx interface by a subscriber, which may include multiple IMPIs, but one IMPI can only belong to one IMS subscription;
One IMPI may include multiple IMPUs, and one IMPU may be shared by multiple IMPIs;
That is to say, the relationship between the IMS subscription and the IMPI is one-to-many, and the relationship between the IMPI and the IMPU is many-to-many.
In the IMS network, after being registered with the network, user equipment (UE) may use various services offered by the IMS network. Meanwhile, the UE may select to subscribe to unregistered services. When the UE has not registered with the network, the network can still provide the user with unregistered services, such as incoming call forwarding and incoming call record.
The current network has a restriction that all the user identities under one IMS subscription will be provided with services by the same S-CSCF. Accordingly, the following problems will occur under the following situations.
(1) When the user has both an unregistered termination request or an unregistered initiation request initiated by the AS instead of the user and a registration request, the unregistered request services will fail if the I-CSCF successively selects different S-CSCFs for the user to provide services.
(2) When the user has two or more unregistered termination requests or unregistered initiation requests initiated by the AS instead of the user, if the I-CSCF successively selects different S-CSCFs for the user to provide services, the second S-CSCF, after requesting user-unregistered service data, will receive a failure response from the HSS indicating that the user with unregistered services cannot be provided.
(3) When multiple terminals of the user all have registered, if the I-CSCF successively selects different S-CSCFs for the user to provide services, after an S-CSCF1 selected in the registration process of the first terminal sends MAR (multimedia authenticate request) request authentication data to the HSS, the HSS will save the name of the S-CSCF1. Before a second registration message of the first terminal reaches the I-CSCF, if an S-CSCF2 selected in the registration process of a second terminal sends MAR request authentication data to the HSS, and the HSS will save the name of the S-CSCF2 and overwrite the name of the S-CSCF1. The successive registration message of the first terminal will be routed to the S-CSCF2. At this time, the first terminal registration will fail because the S-CSCF2 has no user information.